Calendar of Physics Talks Vienna

If the Higgs Mass is … or what might be known by 2016

Speaker:

Dr. Michael Dittmar (ETH Zürich)

Abstract:

After more than 20 years of intense and detailed theoretical calculations and experimental simulations, the prospect to search for a Higgs like boson and to discover it at the 14 TeV LHC and for a given luminosity are well known. The LHC and its experiments have now started to operate at 7 TeV and some encouraging first experimental results, despite the still low luminosity, have already been presented. After a short overview about these first LHC results, the perspectives for direct Higgs searches using a realistic(?) LHC road map up to early 2016 will be presented. Assuming a few representative Higgs masses, implications for its discovery and the consequences for todays experimental constraints and the electroweak precision data will be discussed.

Date:

Mon, 13.09.2010

Time:

16:00

Location:

Institut für Hochenergiephysik, Nikolsdorfergasse 18, 1050 Wien

Contact:

Dr. Josef Strauss

Exploring Chiral Phase Transitions with Probe Branes

Speaker:

Nick Evans (Univ. Southampton)

Abstract:

The D3/D7 and D3/D5 systems are holographic to 4d and 3d strongly coupled gauge theories. Supersymmetry breaking perturbations (such as a magnetic field) induce a quark condensate that breaks chiral symmetry. I use holography to describe their temperature-chemical potential phase diagram. The diagram contains first and second order chiral restoration and separate meson melting transitions joined at a number of critical points. The D3/D5 system displays a Berezinskii-Kosterlitz-Thouless transition (exponential scaling) at T=0 with density. We add an extra phenomenological operator that breaks chiral symmetry that allows us to interpolate between a BKT transition and a mean field second order transition through a range of non-mean field transitions. We can analytically predict the critical exponents in the non-mean-field region by assuming that a one dimensional field theory controls the IR. Finally I will discuss some ongoing work on studying non-equilibrium aspects of these phase transitions.

Date:

Tue, 14.09.2010

Time:

14:00

Duration:

60 min

Location:

Erwin-Schrödinger-Institut, Boltzmann-HS

Contact:

Anton Rebhan, TU Wien

Using energy: Past, Present and in the Future (or what is the energy problem?)

Speaker:

Dr. Michael Dittmar (ETH Zürich)

Abstract:

Todays way of life in the richer countries is based on the use of huge amounts of energy in various forms. This energy is coming mostly from the burning of the limited and non renewable oil, gas and coal reserves. Most development scenarios for the next decades of our civilization assume that an annual worldwide growth in the resource use of a few % per year is unavoidable. While it is widely accepted that oil and other resources are indeed finite, most international organizations pretend that resource limits will not become a problem for the next couple of decades.
However, more and more people start to doubt that the imagined continuous growth of energy usage can continue for much longer. Such views are supported by actual data which show that many oil and gas rich areas are in rapid decline today. Thus, the idea that worldwide supplies of oil and gas are soon approaching a terminal decline, which will be followed by similar coal and uranium resource constraints, is spreading fast.
In this talk we will confront "business as usual" ideas about the coming decades with the latest data about especially oil and uranium resources and explain why nuclear fusion will always be at least 50 years away. Finally some ideas and imaginations about future civilizations functioning with much less available energy will be outlined.

We study a large class of non-supersymmetric gauge theory
operators of the form of a trace times a Schur polynomial - a
convenient description of axially symmetric bubbling solutions which
have a simple representation as Young Tableux. The stringy description
is that of strings excited on a class of 1/2 BPS supergravity
backgrounds. We look at generic, axially symmetric bubbling solutions
corresponding to pure states in the gravity theory and the excitations
upon them. We are able to calculate a reduced density matrix by
integrating out the supersymmetry breaking stringy excitations and
thus calculate the entropy of ensembles of such geometries. This leads
to a new method by which we may be able to understand the microstate
counting of black holes from string theory.

Date:

Wed, 15.09.2010

Time:

14:00

Duration:

60 min

Location:

Erwin-Schrödinger-Institut, Boltzmann-HS

Contact:

Anton Rebhan, TU Wien

Large-N volume independence in conformal and confining gauge theories

Speaker:

Laurence G. Yaffe (Univ. of Washington, Seattle)

Abstract:

Consequences of large N volume independence are examined in conformal and confining gauge theories. In the large N limit, gauge theories compactified on $\R^{d-k} \times (S^1)^k$ are independent of the $S^1$ radii, provided the theory has unbroken center symmetry. In particular, this implies that a large N gauge theory which, on $\R^d$, flows to an IR fixed point, retains the infinite correlation length and other scale invariant properties of the decompactified theory even when compactified on $\R^{d-k} \times (S^1)^k$. In other words, finite volume effects are 1/N suppressed. In lattice formulations of vector-like theories, this implies that numerical studies to determine the boundary between confined and conformal phases may be performed on one-site lattice models. In N=4 supersymmetric Yang-Mills theory, the center symmetry realization is a matter of choice: the theory on $\R^{4-k}\times (S^1)^k$ has a moduli space which contains points with all possible realizations of center symmetry. Large N QCD with massive adjoint fermions and one or two compactified dimensions has a rich phase structure with an infinite number of phase transitions coalescing in the zero radius limit.

Date:

Thu, 16.09.2010

Time:

14:00

Duration:

60 min

Location:

Erwin-Schrödinger-Institut, Boltzmann-HS

Contact:

Anton Rebhan, TU Wien

Fast and Parallel Event Reconstruction in the CBM Experiment (FAIR/GSI)

Speaker:

Dr. Ivan Kisel (GSI, Darmstadt, Germany)

Abstract:

On-line event reconstruction is one of the most challenging problems of data analysis in modern
high-energy physics experiments, which have to process per second of the order of 107 events
with high track multiplicity and density, registered by detectors of dierent types and, in many
cases, located in non-homogeneous magnetic eld. This is especially important for heavy-ion
experiments, like CBM, a future xed-target heavy-ion experiment at FAIR/GSI with up to
thousand of tracks per central collision.
Usually track nding is the most time consuming part of the event reconstruction. Every track
nder has to deal with a very specic and complicated combinatorial optimization process
of collecting one- or two-dimensional measurements into ve-dimensional tracks. The cellular
automaton method benets from building of cells, short track elements, with higher than
measurements dimensionality before starting the combinatorial search. The method is intrinsically
local, operating on data only in close neighborhood. In addition, the algorithm based on the
cellular automaton method is well suited for parallelism.
On-line processing of large data volumes requires using the maximum capabilities of modern and
future many-core CPU and GPU architectures. One of such powerful features is a SIMD (Single
Instruction, Multiple Data) instruction set, which allows packing several data items in one register
and to operate on all of them, thus achieving more operations per clock cycle. Motivated by the idea
of using the SIMD unit of modern processors, the Kalman lter based track t has been adapted for
parallelism, including memory optimization, numerical analysis, vectorization with inline operator
overloading, and optimization using software development kits. More details on parallelism of the
event reconstruction algorithms will be presented and discussed.